Self-monitored fluid pressure booster system

ABSTRACT

A booster for a fluid pressure operated system in which relatively low pressure is used in the system and the booster is designed to be positioned immediately adjacent the fluid operated mechanism so as to eliminate the need for high pressure fittings and components. The booster has a spool which is shiftable in response to pressure build up in the mechanism. The spool acts as a sliding valve to direct fluid flow through a pressure converter such as a turbine or volumetric motor-pump located inside the spool.

This invention relates to the field of fluid pressure operated devices,particularly hydraulically operated tools, arms, motors, etc. Itparticularly pertains to a device for "on the spot" boosting ofhydraulic pressure so that an entire system does not need to bemaintained at a high pressure which is only needed at the point ofoperation of a fluid pressure operated mechanism.

In many applications of fluid pressure operated mechanisms it isnecessary to apply a relatively low pressure during part of theoperation and a relatively high pressure for a shorter period during theoperation. The relatively high pressure can be obtained from a separatesource of pressure, by maintaining the entire system at the higherpressure, or by a pressure booster which operates only when the higherpressure is needed. Generally speaking there has been a tendency toincrease the fluid pressure used to operate various types of mechanisms,such as hydraulic cylinders or motors. For example, a pressure of 1,500PSI was formerly considered to be high, but now it is not uncommon tohave a pressure of 3,000 PSI or greater. This can lead to more compactcomponents operating on a system with perhaps a smaller fluid reserve,but, it also leads to all of the components being more delicate,therefore more difficult and expensive to manufacture and requiring highquality maintenance.

Although increasingly sophisticated components, such as valves andmulti-stage pumps are available for use with these higher pressures,there is some standard equipment which cannot be used at pressures abovesay about 2000 PSI, such as single stage gear pumps.

For installations where it is desirable to have a high volume-lowpressure fluid flow in the initial stages of movement and then, as theload increases, to have a high pressure fluid which can be utilized at alower volume flow, various types of pressure boosters are used asaccessories in a basic hydraulic system, requiring specialized andexpensive components in the high pressure portion thereof. Such mixedsystems have generally not proved very satisfactory and often after apartial conversion a system owner may conclude it would be better tostart over with a complete high pressure system despite thedisadvantages described above. There is thus a need for a better meansto enable utilization of relatively low pressure throughout a systemexcept at the very point of pressure consumption, eliminating the needfor high pressure valves and fittings between the booster and consumingdevice and permitting the use of components comparable in size or evensmaller than those used in high pressure systems. Similarly such apressure booster should be self-monitoring that is, to become actuatedonly when the higher pressure is required and to permit free flowthrough under lower (unboosted) pressure when not needed.

It is thus an object of the present invention to provide an integratedself-monitored fluid pressure booster device or system which is morecompact than existing systems and can be mounted immediately adjacentthe fluid operated mechanism so as to eliminate the need for highpressure parts between the booster and the mechanism.

It is further an object to provide a device in which the unobstructedfull flow of fluid is available to feed a mechanism when boostedpressure is not required but to automatically provide higher pressurewhen needed by the mechanism.

In order to describe a preferred embodiment the remainder of thisdescription will be directed to the construction and use of aself-monitored fluid pressure booster which is adapted to be secureddirectly to the end of a hydraulic cylinder or ram, for example, a ramwhich would be used to travel a relatively long distance in which littleresistance was encountered, such as one which is used to cut anautomobile body in two but would meet with high resistance, and requirehigh pressure, only in the last few inches of travel near the end of thestroke.

This preferred embodiment will now be described in connection with theattached figures of drawings which are furnished by way of example andnot limitation in which further advantages and objects will becomeapparent:

FIG. 1 is a perspective overall view of a hydraulic system showing thebooster of this invention at one end of a hydraulic cylinder:

FIG. 2 is a schematic representation of the system shown in FIG. 1;

FIG. 3 is a sectional view through the booster of the present inventionshowing the use of an axial flow turbine and pump as the pressureconverter, the converter being located in a shiftable spool which isillustrated to show the fluid flow by-passing the converter;

FIG. 4 is a sectional view similar to FIG. 3 but with a shiftable spoolin a position where the fluid flow is directed through the pressureconverter;

FIG. 5 is a sectional view similar to FIG. 3 but illustrating the use ofa gear motor-pump as the pressure converter;

FIG. 6 is a sectional view similar to FIG. 4 but illustrating the use ofa gear motor-pump as the pressure converter;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 6;

FIG. 8 is a sectional view taken along line 8--8 of FIG. 6;

FIG. 9 is a perspective view, partly in section, of the booster shown inFIGS. 3 and 4.

Turning now to the drawings in greater detail, FIG. 1 illustrates agenerally conventional hydraulic cylinder and actuating circuit having areservoir to hold the fluid, a motor to drive a pump P to force fluidunder pressure into a directional valve where it can be shifted toactuate the piston either inwardly or outwardly in relation to itscylinder. At the end of the cylinder is mounted the booster 10 which isthe object of the present invention.

FIG. 2 illustrates a setup similar to that of FIG. 1 but where theworking cylinder and booster are located at a distance from thereservoir, pump and directional valve, usually by means of flexiblehoses. In such a setup it is, of course, desirable to expose theflexible hoses only to low pressure so as to not only preserve theirlife, but also to permit the use of less expensive hoses andconnections.

FIG. 3 shows only a portion of the hydraulic cylinder 14, that cylinderhaving a threaded portion 13 between the body 12 of the booster 10 andthe cylinder. The body 12 has inlet port means 16 and outlet port means18 each with a threaded hose or pipe connection in the outer portionthereof. The body has a bore 20 preferably centrally located with anaxially shiftable spool 22 positioned therein. A series of webs in thebody define annular flow passages in the body, these webs being axiallypositioned so as to define different flow paths either through or aroundthe shiftable spool 22 depending upon the axial position of that spool.The spool and bore are machined with a close fitting tolerance betweenmating surfaces so that a substantially fluid-tight seal can be effectedbetween them. The bore and spool are preferably circular in crosssection. In FIG. 3 the web 24 is axially narrower than the inlet passageopening 26 of the shiftable spool, thus defining a by-pass flow path sothat substantially all of the incoming fluid in port means 16 will flowdirectly into cylinder 14 rather than through spool 22 or into theoutlet port means 18. In the position shown in FIG. 3 the outlet portmeans 18 is closed off from fluid flow because shoulder 70 of the spoolcontacts web 41 of the body.

Thus, the flow of fluid through the by-pass flow path as indicated bythe arrows in FIG. 3 will continue until pressure begins to build up inthe cylinder 14. When this pressure gets sufficiently high, the entirespool 22 will shift within the bore 20 to the right as illustrated inFIG. 3. The spool will then assume the position shown in FIG. 4 thusdefining different flow paths for the fluid through the body. The effectof these flow paths will be discussed in connection with FIG. 4.

The shifting of the spool 22 is controlled by several factors. At thedistal end of the spool is a return means, the present drawingsillustrating a spring-dashpot arrangement. It is contemplated that thereturn means could be in a variety of forms including manual actuation,separate fluid operated means, or electromechanical devices. In thepresently illustrated preferred embodiment a spring 28 is held incompression between an adjusting screw 30 and washer 32 and the end ofthe spool. The spring tends to bias the spool 22 toward the left inFIGS. 3 and 4. When the back pressure in the cylinder 14 becomes strongenough to overcome the effect of spring 28, the spool 22 will shift tothe right as shown in FIG. 4 with the dashpot 34 acting to control thespeed of the shifting movement so as to prevent hammering or rapidunstable shifting of the spool.

The dashpot 34 is defined by an annular web 39 presenting a cylinderwall 40 which is engaged by a cylinder ring 36 on an extension 33 of thespool, the ring 36 being held in place by a spring retainer ring 38. Theopening 42 through which the extension 33 of the spool projects inslightly larger in diameter than that projection for reasons which willbe explained in connection with FIG. 4. The amount of force required toshift spool 22 is controlled by several factors: the strength of spring28, the fit of cylinder ring 36, and a passageway 44 extending throughthe center of the spool. Because of the passageway 44 the fluid pressureon both sides of the spool is equal, however, the area upon which thatpressure is acting is unequal since the diameter at the spool at point46 is greater than the diameter at cylinder ring 36. Thus the size ofthe return spring can be calculated as follows:

    F ≦ (A.sub.1 - A.sub.2) P.sub.1

where:

F = force of spring

A₁ = larger area of spool (at diameter 46)

A₂ = smaller area of spool (at cylinder ring 36)

P₁ = maximum pressure in inlet port means

The speed of the shifting of the spool is controlled by the size of theorifice 48 in passageway 44. When the spool shifts there will be a fluidflow through passageway 44 in a direction opposite to that of the spool;the speed of that flow (and consequently the speed of the shifting) iscontrolled by the size of orifice 48, a larger orifice leading to fastershifting.

When the back pressure in cylinder 14 becomes sufficently high it willforce the spool 22 to shift to assume the position illustrated in FIG.4. In that position the fluid flow path is completely changed with web24 fitting the shoulder 46 at maximum diameter of the spool 22 so as toforce substantially all of the incoming fluid into the inlet passage 26of the shifter with the shoulders 46 and 70 acting as means to controlthe fluid flow in the manner of a sliding valve. The incoming fluid flowwill then be divided, part of it following the path of least resistancepast stator vanes 50 which imparts a rotary motion to the fluid which inturn forces rotor blades 52 to rotate. This rotation causes the entireturbine rotor 56 to turn thus rotating turbine pump rotor blades 58which are spaced between stator vanes 60. The interaction of the blades58 and vanes 60 is that of an axial flow pump which forces part of theincoming fluid from inlet port 16 therethrough to emerge at considerablyhigher pressure into cylinder 14. This supplies the higher pressurerequired by the cylinder ram when it needs to exert maximum forces. Theturbine rotor 56 is supported for rotary movement in sets of bearings,preferably roller bearings 62 and 64. Since the back pressure incylinder 14 would tend to force rotor 56 toward bearings 64, a smallpressure bleedoff passage 66 extends at an angle from passageway 44 soas to place an area 68 located between the rotor and the remainder ofthe spool at the boosted pressure thus holding the rotor in approximatelongitudinal equilibrium. This can be achieved by controlling the sizeof area 68 in such a way that area 68 multiplied by the boosted pressureis equal to or larger than the total axial reaction force on rotor 44.As previously described, when the spool is shifted to the position shownin FIG. 4, the incoming fluid is split into two portions, one goingthrough the pump vanes and blades 58-60 and the other through motorvanes and blades 50-52. Upon being discharged from blades 52 theoutgoing fluid then enters an annular portion of outlet port means 18 asdefined between webs 39 and 41. Due to the shifting of spool 22 shoulder70 has now moved over sufficiently far to the right so that outgoingfluid from the motor is in direct communication with the outlet port 18.As can be seen from the foregoing the turbine motor-pump can then act asa pressure converter to change the high volume-low pressure incomingflow into a high pressure-low volume flow in that portion which isdischarged into cylinder 14. Shortly after the spool 22 shifts aconsiderable portion of the fluid may be diverted into the cylinder 14.However, as the back pressure increases, that volume will be reduced,forcing a greater proportion of the fluid through the motor 50-52. Thishas the effect of running the turbine faster and thus increasing thepressure output of the pump blades 58-60. If additional pressure isneeded it can be obtained by increasing the number of stages in eitheror both of the motor or pump. A two-stage motor and a four-stage pumphave been used here only for purposes of illustration. When the backpressure in cylinder 14 decreases to less than that from incomingpressure from pump P the spring 28 will then return the spool 22 to theposition shown in FIG. 3. The speed of the return movement is alsocontrolled by the dashpot 34 because the area 72 between the web 39 andcylinder ring 36 is filled with fluid due to the clearance 74 betweenthe extension 33 and the web 39. This clearance 74 acts in a mannersimilar to the orifice 48 to control the speed of the spool shifter, thegreater the clearance, the faster the return shift can take place.

As can be seen the foregoing there are no check valves or othercomponents in the high pressure part of the system. High pressure existsonly between the pump blades and the cylinder itself thus eliminating amajor source of possible difficulty in construction and maintainence ofa fluid boosted pressure system.

FIG. 9 better illustrates the construction of spool 22 showing itshifted to the same active position as in FIG. 4, with the flow paththrough the spool to rotate the turbine motor-pump. As shown in FIG. 9the spool has a plurality of openings 94 between webs 95 for the passageof fluid into and out of the spool. The spool is constructed to beopened up along either an axial or longitudinal joint for insertion orservicing of the turbine and its blades or bearings.

Turning now to FIGS. 5 through 8, FIG. 5 is a sectional view similar toFIG. 3 but taken at 90° thereto so that the inlet and outlet port meansof the body are not shown but to give a better idea of the remainder ofthe body 12. FIGS. 5-8 also illustrate an alternative form of pressureconverter using a volumetic pump and motor such as a gear motor-pumprather than a turbine. Only parts which are different will be separatelydescribed.

The operation of the spool--to shift in response to a pressure build upin the cylinder--remains the same as does the arrangement of inlet andoutlet ports and passages with the spool acting as a sliding valve tocontrol the flow of fluid through them.

The operation of the dashpot also remains the same; FIG. 5 includesillustration of an optional cylinder pressure signal 76 which has apassageway 78 to conduct fluid under pressure through a conduit 80 to apressure gauge, signal device or pressure control valve to remotelycontrol bleeding of dash-pot 34 to shift spool. This pressure signal maybe also used with the embodiment of FIGS. 3-4.

In the gear motor-pump pressure converter incoming fluid enters inletport means 16 of body 12 and in FIG. 5 by-passes the spool in the samemanner as in FIG. 3. After sufficient pressure buildup in cylinder 14the back pressure will cause the spool to shift to the position shown inFIG. 6. In FIG. 6 the incoming fluid flow is divided with part of itgoing to the left of partition 82 to gear pump 84 and part of it goingto the right of partition 82 to gear motor 86. The fluid flow throughthe gear motor causes rotation of gears 90 which in turn rotate shafts86 and 87. These shafts extend through partition 82 and support pumpgears 92 for rotation as shown in FIG. 7. That portion of the fluidwhich goes into the pump is then increased in pressure through theaction of the pump and then discharged into cylinder 14. The passages ofthe motor and of the pump are of conventional construction to direct thefluid through the housing 96, around the gears and into the outlet portmeans 18 in the case of fluid going to the motor or into the mechanism14 in the case of fluid going to the pump.

The volumetric motor-pump is advantageous over the turbine for holding ahydraulic ram in an extended position with a minimum amount of fluidflow to it during the holding operation due to the fact that it is verydifficult for any fluid to flow backward through a gear pump or motor.To insure a positive hold a check valve (not shown) would be used in theinlet port means. To achieve higher pressure and tighter holding it iscontemplated that another type of volumetric motor-pump such as a pistonmotor and pump combination could be used. It is to be noted that thecheck valve while only retaining pressure A at the inlet port, isinsuring full boosted pressure holding at the mechanism or motor port.

Volumetric motors and pumps would be mostly used for lower boostingvolume needs and when the basic hydraulic system flow must be divertedpartially or completely to other tasks while the high pressure ismaintained in the mechanism 14. The turbine type motor and pump will bepreferable when the full power of the basic system has to be convertedto higher pressure to achieve maximum work output by the mechanism underhigh boosted pressure conditions.

Cascades of two or more self-monitored boosters can be connected inseries so that the over all system can be used more efficiently in theintermediate pressure range between the low basic system pressure andthe maximum boosted pressure.

It is also contemplated that the spool could be a different type ofsliding means such as a poppet valve assembly having a frusto-conicalseat to effect the sealing between the sliding means or spool and thebody.

Although various specific embodiments have been described in detail toteach those skilled in the art to use this invention, they are by way ofexample only, and the scope of the invention is defined by the followingclaims.

I claim:
 1. A self-monitored fluid pressure booster device comprising:a.a body having a bore connectable to a fluid pressure operated mechanismand inlet port means and outlet port means connected to the bore; b. ashiftable sliding means in the bore having means to control fluid flowto and from said outlet and inlet port means in response to pressure inthe fluid operated mechanism; c. pressure converter means associatedwith said sliding means to convert a high volume low pressure fluid flowinto a low volume high pressure flow; d. said sliding means beingmounted to shift from a first position in which the fluid control meansdirects the fluid flow from the inlet port into the mechanism to asecond position in which the fluid control means directs the fluid flowfrom the inlet port through the pressure converter means to themechanism and the outlet port means.
 2. The device of claim 1 includingmeans to return the sliding means from said second position to saidfirst position.
 3. The device of claim 2 in which the pressure convertermeans has a fluid passage therethrough to interconnect the return meanswith the area of boosted pressure.
 4. The device of claim 2 in which thereturn means is biased to operate in response to a change in pressure inthe fluid operated mechanism.
 5. The device of claim 2 in which thereturn means is a spring and dashpot means cooperating with one end ofthe sliding means.
 6. The device of claim 1 in which the pressureconverter means is a turbine type pump and motor.
 7. The device of claim1 in which the pressure converter means is a volumetric type pump andmotor.
 8. The device of claim 7 in which the volumetric pump and motorare a gear pump and motor.
 9. A self-monitored fluid pressure boosterdevice comprising:a. a body having a bore with connection means at oneend for connection to a fluid pressure operated mechanism, inlet portmeans and outlet port means in the body axially spaced along andcommunicating with the bore; b. a shiftable sliding means in the borehaving pressure converter means mounted therein the pressure convertermeans having a motor and pump, the sliding means having an outletpassage from the motor, a discharge passage communicating the pump tosaid connection means and an inlet passage connected to the motor andthe pump; c. said sliding means being mounted for axial shifting alongthe bore from a first inactive position in which the inlet port means isconnected for fluid to flow directly to the mechanism and the outletpassage are blocked to a second active position in which the inlet portmeans is aligned with the inlet passage and the outlet port means isaligned with the outlet passage so that fluid pressure in the inlet portmeans will cause fluid to flow through the inlet passage to both themotor and the pump, the motor driving the pump to create a zone ofboosted pressure in the discharge passage, the shifting of the slidingmeans being a response to the pressure in said zone.
 10. The device ofclaim 9 including means to return the sliding means from said secondposition to said first position.
 11. The device of claim 10 in which thepressure converter means has a fluid passage therethrough tointerconnect the return means with the area of boosted pressure.
 12. Thedevice of claim 10 in which the return means is biased to operate inresponse to a change in pressure in the fluid operated mechanism. 13.The device of claim 10 in which the return means is a spring and dashpotmeans cooperating with one end of the sliding means.
 14. The device ofclaim 9 in which the pressure converter means is a turbine type pump andmotor.
 15. The device of claim 9 in which the pressure converter meansis a volumetric type pump and motor.
 16. The device of claim 15 in whichthe volumetric type pump and motor is a gear pump and motor.
 17. Aself-monitored fluid pressure booster device comprising:a. a body havinga circular bore with one end being open to present connection means toattach the body to a fluid pressure operated mechanism, an inlet portand an outlet port in the body axially spaced along and communicatingwith the bore; b. a cylindrical sliding means in the bore mounted foraxial shifting, a pressure converter in the sliding means having a fluidoperated motor directly connected to a fluid pump, an outlet passagefrom the motor, a discharge passage from the pump to the area of theconnection means and an inlet passage connected to both the motor andthe pump; c. a first shoulder on the sliding means adjacent the inletpassage and a second shoulder on the sliding means adjacent the outletpassage; d. the inlet and outlet ports in the body being positioned inrelation to said shoulders so that in a first axially shifted positionthe first shoulder permits passage of fluid directly from the inlet portto the area of the connection means and the second shoulder blocks offthe outlet passage and in a second axially shifted position the firstshoulder blocks off direct fluid flow from the inlet port to the area ofthe connection means, directing the fluid flow from the inlet port tothe inlet passage of the sliding means and the second shoulder ispositioned to permit fluid flow from the outlet passage of the slidingmeans to the outlet port of the body; e. a cylindrical extension fromthe sliding means on the end opposite the pump, said extension being ofsmaller diameter than said first shoulder; f. a cylindrical cavity inthe body positioned to receive said extension therein; g. sealing meansbetween said extension and said cavity to define a dashpot to dampen theshifting of the sliding means; h. biasing means in said dashpot tendingto return the sliding means to said first position upon a decrease inpressure in the area of said connection means.
 18. The device of claim17 in which the pressure converter means is a turbine type pump andmotor.
 19. The device of claim 17 in which the pressure converter meansis a volumetric type pump and motor.
 20. The device of claim 19 in whichthe volumetric type pump and motor is a gear pump and motor.
 21. Thedevice of claim 1 in which the pressure converter means is locatedwithin said shiftable sliding means. .Iadd.
 22. The device of claim 1 inwhich the fluid flow in said second position passes directly from saidinlet port means to said pressure converter means. .Iaddend. .Iadd. 23.A fluid pressure operated system comprising:pump means to supply a fluidflow under a low pressure and a high volume; a fluid operated mechanism;a self monitored fluid pressure booster device in communication withsaid pump and said mechanism, said device comprising: a body having abore in direct fluid communication with said fluid pressure operatedmechanism; inlet port means connected to the pump means, and outlet portmeans, a shiftable sliding means for controlling fluid flow from saidinlet port means; pressure converter means associated with said slidingmeans to convert said low pressure - high volume fluid flow to a highpressure - low volume fluid flow; said sliding means being mounted toshift in response to pressure in the operated mechanism from a firstposition in which the means for controlling the fluid flow permits afree flow of the fluid from the inlet port into and out of the operatedmechanism to a second position in which the means for controlling thefluid flow directs a portion of the fluid flow from the inlet portthrough the pressure converter means directly to the mechanism, andanother portion to the outlet port means; said converter means beingconnected directly to said operated mechanism so that only said boosterdevice and the operated mechanism are subjected to said high pressure -low volume flow. .Iaddend..Iadd.
 24. The system of claim 23 in which theshiftable sliding means is itself shaped to provide means forcontrolling the fluid flow. .Iaddend. .Iadd.
 25. The system of claim 23including a reservoir, and a 3 way directional control valve interposedbetween the pump and the booster device and connected to said reservoirso that in a first position fluid is fed directly from the pump, throughthe valve to the booster device, and in a second position fluid flowfrom the pump to the booster is cut off and the booster device iscommunicated to the reservoir. .Iaddend. .Iadd.
 26. The system of claim25 including means connecting the directional control valve to theopposite end of the fluid operated mechanism and wherein in said secondposition said pump is communicated with said opposite end of the fluidoperated mechanism. .Iaddend.